Tone production of classical guitar performance is an essential part for musicians to transmit their sentimental and interpretative intentions. This work investigates subjective preferences of two common plucking techniques used by guitar players, apoyando (rest) and tirando (free) strokes. Six excerpts of classical guitar music with different tempos and range of frequency were performed using the two techniques and were recorded for the subjective tests. Two groups of subjects, guitar players and people who do not play guitar, were investigated to see if both groups evaluate the guitar timbre in different way or not. AB test was conducted with 50 persons for each group asking which technique is preferred and have more sound quality. Then the harmonic components and autocorrelation function (ACF) of each stroke were analysed to relate with the characteristics of the music program (tempo and frequency range) and subjective preferences. The effective duration of ACF is defined with the taue (τe) parameter. Results of the subjective test showed that harmonic content did not define preferences, but higher taue values of the ACF were correlated with a higher sound guitar quality.